enhance memory_write metadata and add /lang command

pkg/tools/memory_write_test.go

@@ -0,0 +1,28 @@
+package tools
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestFormatMemoryLine(t *testing.T) {
+	got := formatMemoryLine("remember this", "high", "user", []string{"preference", "lang"})
+	if got == "" {
+		t.Fatal("empty formatted line")
+	}
+	if want := "importance=high"; !strings.Contains(got, want) {
+		t.Fatalf("expected %q in %q", want, got)
+	}
+	if want := "source=user"; !strings.Contains(got, want) {
+		t.Fatalf("expected %q in %q", want, got)
+	}
+}
+
+func TestNormalizeImportance(t *testing.T) {
+	if normalizeImportance("HIGH") != "high" {
+		t.Fatal("expected high")
+	}
+	if normalizeImportance("unknown") != "medium" {
+		t.Fatal("expected medium fallback")
+	}
+}